/*
 * Copyright 2019-2020 Shawn Peng
 * Email: shawnpeng@yeah.net
 * <p>
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 * <p>
 * http://www.apache.org/licenses/LICENSE-2.0
 * <p>
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package com.quantworld.app.utils;

import java.io.UnsupportedEncodingException;

public class Base64 {
  /**
   * Chunk size per RFC 2045 section 6.8.
   *
   * <p>
   * The {@value} character limit does not count the trailing CRLF, but counts
   * all other characters, including any equal signs.
   * </p>
   *
   * @see <a href="http://www.ietf.org/rfc/rfc2045.txt">RFC 2045 section
   * 6.8</a>
   */
  static final int CHUNK_SIZE = 76;

  /**
   * Chunk separator per RFC 2045 section 2.1.
   *
   * @see <a href="http://www.ietf.org/rfc/rfc2045.txt">RFC 2045 section
   * 2.1</a>
   */
  static final byte[] CHUNK_SEPARATOR = "\r\n".getBytes();

  /**
   * The base length.
   */
  static final int BASELENGTH = 255;

  /**
   * Lookup length.
   */
  static final int LOOKUPLENGTH = 64;

  /**
   * Used to calculate the number of bits in a byte.
   */
  static final int EIGHTBIT = 8;

  /**
   * Used when encoding something which has fewer than 24 bits.
   */
  static final int SIXTEENBIT = 16;

  /**
   * Used to determine how many bits data contains.
   */
  static final int TWENTYFOURBITGROUP = 24;

  /**
   * Used to get the number of Quadruples.
   */
  static final int FOURBYTE = 4;

  /**
   * Used to test the sign of a byte.
   */
  static final int SIGN = -128;

  /**
   * Byte used to pad output.
   */
  static final byte PAD = (byte) '=';

  // Create arrays to hold the base64 characters and a
  // lookup for base64 chars
  private static byte[] base64Alphabet = new byte[BASELENGTH];
  private static byte[] lookUpBase64Alphabet = new byte[LOOKUPLENGTH];

  // Populating the lookup and character arrays
  static {
    for (int i = 0; i < BASELENGTH; i++) {
      base64Alphabet[i] = (byte) -1;
    }
    for (int i = 'Z'; i >= 'A'; i--) {
      base64Alphabet[i] = (byte) (i - 'A');
    }
    for (int i = 'z'; i >= 'a'; i--) {
      base64Alphabet[i] = (byte) (i - 'a' + 26);
    }
    for (int i = '9'; i >= '0'; i--) {
      base64Alphabet[i] = (byte) (i - '0' + 52);
    }

    base64Alphabet['+'] = 62;
    base64Alphabet['/'] = 63;

    for (int i = 0; i <= 25; i++) {
      lookUpBase64Alphabet[i] = (byte) ('A' + i);
    }

    for (int i = 26, j = 0; i <= 51; i++, j++) {
      lookUpBase64Alphabet[i] = (byte) ('a' + j);
    }

    for (int i = 52, j = 0; i <= 61; i++, j++) {
      lookUpBase64Alphabet[i] = (byte) ('0' + j);
    }

    lookUpBase64Alphabet[62] = (byte) '+';
    lookUpBase64Alphabet[63] = (byte) '/';
  }

  private static boolean isBase64(byte octect) {
    if (octect == PAD) {
      return true;
    } else if (base64Alphabet[octect] == -1) {
      return false;
    } else {
      return true;
    }
  }

  public static void main(String[] args) {
    String decodestr = new String(decode("MTE2LjQ2Mzg0NzU1MDg0".getBytes()));
    System.out.println(decodestr);
  }

  /**
   * Tests a given byte array to see if it contains only valid characters
   * within the Base64 alphabet.
   *
   * @param arrayOctect byte array to test
   * @return true if all bytes are valid characters in the Base64 alphabet or
   * if the byte array is empty; false, otherwise
   */
  public static boolean isArrayByteBase64(byte[] arrayOctect) {

    arrayOctect = discardWhitespace(arrayOctect);

    int length = arrayOctect.length;
    if (length == 0) {
      // shouldn't a 0 length array be valid base64 data?
      // return false;
      return true;
    }
    for (int i = 0; i < length; i++) {
      if (!isBase64(arrayOctect[i])) {
        return false;
      }
    }
    return true;
  }

  /**
   * Encodes binary data using the base64 algorithm but does not chunk the
   * output.
   *
   * @param binaryData binary data to encode
   * @return Base64 characters
   */
  public static byte[] encodeBase64(byte[] binaryData) {
    return encodeBase64(binaryData, false);
  }

  /**
   * Encodes binary data using the base64 algorithm and chunks the encoded
   * output into 76 character blocks
   *
   * @param binaryData binary data to encode
   * @return Base64 characters chunked in 76 character blocks
   */
  public static byte[] encodeBase64Chunked(byte[] binaryData) {
    return encodeBase64(binaryData, true);
  }

  /**
   * Decodes a byte[] containing containing characters in the Base64 alphabet.
   *
   * @param pArray A byte array containing Base64 character data
   * @return a byte array containing binary data
   */
  public static byte[] decode(byte[] pArray) {
    return decodeBase64(pArray);
  }

  /**
   * Encodes binary data using the base64 algorithm, optionally chunking the
   * output into 76 character blocks.
   *
   * @param binaryData Array containing binary data to encode.
   * @param isChunked  if isChunked is true this encoder will chunk the base64 output
   *                   into 76 character blocks
   * @return Base64-encoded data.
   */
  public static byte[] encodeBase64(byte[] binaryData, boolean isChunked) {
    int lengthDataBits = binaryData.length * EIGHTBIT;
    int fewerThan24bits = lengthDataBits % TWENTYFOURBITGROUP;
    int numberTriplets = lengthDataBits / TWENTYFOURBITGROUP;
    byte encodedData[] = null;
    int encodedDataLength = 0;
    int nbrChunks = 0;

    if (fewerThan24bits != 0) {
      // data not divisible by 24 bit
      encodedDataLength = (numberTriplets + 1) * 4;
    } else {
      // 16 or 8 bit
      encodedDataLength = numberTriplets * 4;
    }

    // If the output is to be "chunked" into 76 character sections,
    // for compliance with RFC 2045 MIME, then it is important to
    // allow for extra length to account for the separator(s)
    if (isChunked) {

      nbrChunks = (CHUNK_SEPARATOR.length == 0 ? 0 : (int) Math
          .ceil((float) encodedDataLength / CHUNK_SIZE));
      encodedDataLength += nbrChunks * CHUNK_SEPARATOR.length;
    }

    encodedData = new byte[encodedDataLength];

    byte k = 0, l = 0, b1 = 0, b2 = 0, b3 = 0;

    int encodedIndex = 0;
    int dataIndex = 0;
    int i = 0;
    int nextSeparatorIndex = CHUNK_SIZE;
    int chunksSoFar = 0;

    // log.debug("number of triplets = " + numberTriplets);
    for (i = 0; i < numberTriplets; i++) {
      dataIndex = i * 3;
      b1 = binaryData[dataIndex];
      b2 = binaryData[dataIndex + 1];
      b3 = binaryData[dataIndex + 2];

      // log.debug("b1= " + b1 +", b2= " + b2 + ", b3= " + b3);

      l = (byte) (b2 & 0x0f);
      k = (byte) (b1 & 0x03);

      byte val1 = ((b1 & SIGN) == 0) ? (byte) (b1 >> 2)
          : (byte) ((b1) >> 2 ^ 0xc0);
      byte val2 = ((b2 & SIGN) == 0) ? (byte) (b2 >> 4)
          : (byte) ((b2) >> 4 ^ 0xf0);
      byte val3 = ((b3 & SIGN) == 0) ? (byte) (b3 >> 6)
          : (byte) ((b3) >> 6 ^ 0xfc);

      encodedData[encodedIndex] = lookUpBase64Alphabet[val1];
      // log.debug( "val2 = " + val2 );
      // log.debug( "k4   = " + (k<<4) );
      // log.debug( "vak  = " + (val2 | (k<<4)) );
      encodedData[encodedIndex + 1] = lookUpBase64Alphabet[val2
          | (k << 4)];
      encodedData[encodedIndex + 2] = lookUpBase64Alphabet[(l << 2)
          | val3];
      encodedData[encodedIndex + 3] = lookUpBase64Alphabet[b3 & 0x3f];

      encodedIndex += 4;

      // If we are chunking, let's put a chunk separator down.
      if (isChunked) {
        // this assumes that CHUNK_SIZE % 4 == 0
        if (encodedIndex == nextSeparatorIndex) {
          System.arraycopy(CHUNK_SEPARATOR, 0, encodedData,
              encodedIndex, CHUNK_SEPARATOR.length);
          chunksSoFar++;
          nextSeparatorIndex = (CHUNK_SIZE * (chunksSoFar + 1))
              + (chunksSoFar * CHUNK_SEPARATOR.length);
          encodedIndex += CHUNK_SEPARATOR.length;
        }
      }
    }

    // form integral number of 6-bit groups
    dataIndex = i * 3;

    if (fewerThan24bits == EIGHTBIT) {
      b1 = binaryData[dataIndex];
      k = (byte) (b1 & 0x03);
      // log.debug("b1=" + b1);
      // log.debug("b1<<2 = " + (b1>>2) );
      byte val1 = ((b1 & SIGN) == 0) ? (byte) (b1 >> 2)
          : (byte) ((b1) >> 2 ^ 0xc0);
      encodedData[encodedIndex] = lookUpBase64Alphabet[val1];
      encodedData[encodedIndex + 1] = lookUpBase64Alphabet[k << 4];
      encodedData[encodedIndex + 2] = PAD;
      encodedData[encodedIndex + 3] = PAD;
    } else if (fewerThan24bits == SIXTEENBIT) {

      b1 = binaryData[dataIndex];
      b2 = binaryData[dataIndex + 1];
      l = (byte) (b2 & 0x0f);
      k = (byte) (b1 & 0x03);

      byte val1 = ((b1 & SIGN) == 0) ? (byte) (b1 >> 2)
          : (byte) ((b1) >> 2 ^ 0xc0);
      byte val2 = ((b2 & SIGN) == 0) ? (byte) (b2 >> 4)
          : (byte) ((b2) >> 4 ^ 0xf0);

      encodedData[encodedIndex] = lookUpBase64Alphabet[val1];
      encodedData[encodedIndex + 1] = lookUpBase64Alphabet[val2
          | (k << 4)];
      encodedData[encodedIndex + 2] = lookUpBase64Alphabet[l << 2];
      encodedData[encodedIndex + 3] = PAD;
    }

    if (isChunked) {
      // we also add a separator to the end of the final chunk.
      if (chunksSoFar < nbrChunks) {
        System.arraycopy(CHUNK_SEPARATOR, 0, encodedData,
            encodedDataLength - CHUNK_SEPARATOR.length,
            CHUNK_SEPARATOR.length);
      }
    }

    return encodedData;
  }

  /**
   * Decodes Base64 data into octects
   *
   * @param base64Data Byte array containing Base64 data
   * @return Array containing decoded data.
   */
  public static byte[] decodeBase64(byte[] base64Data) {
    // RFC 2045 requires that we discard ALL non-Base64 characters
    base64Data = discardNonBase64(base64Data);

    // handle the edge case, so we don't have to worry about it later
    if (base64Data.length == 0) {
      return new byte[0];
    }

    int numberQuadruple = base64Data.length / FOURBYTE;
    byte decodedData[] = null;
    byte b1 = 0, b2 = 0, b3 = 0, b4 = 0, marker0 = 0, marker1 = 0;

    // Throw away anything not in base64Data

    int encodedIndex = 0;
    int dataIndex = 0;
    {
      // this sizes the output array properly - rlw
      int lastData = base64Data.length;
      // ignore the '=' padding
      while (base64Data[lastData - 1] == PAD) {
        if (--lastData == 0) {
          return new byte[0];
        }
      }
      decodedData = new byte[lastData - numberQuadruple];
    }

    for (int i = 0; i < numberQuadruple; i++) {
      dataIndex = i * 4;
      marker0 = base64Data[dataIndex + 2];
      marker1 = base64Data[dataIndex + 3];

      b1 = base64Alphabet[base64Data[dataIndex]];
      b2 = base64Alphabet[base64Data[dataIndex + 1]];

      if (marker0 != PAD && marker1 != PAD) {
        // No PAD e.g 3cQl
        b3 = base64Alphabet[marker0];
        b4 = base64Alphabet[marker1];

        decodedData[encodedIndex] = (byte) (b1 << 2 | b2 >> 4);
        decodedData[encodedIndex + 1] = (byte) (((b2 & 0xf) << 4) | ((b3 >> 2) & 0xf));
        decodedData[encodedIndex + 2] = (byte) (b3 << 6 | b4);
      } else if (marker0 == PAD) {
        // Two PAD e.g. 3c[Pad][Pad]
        decodedData[encodedIndex] = (byte) (b1 << 2 | b2 >> 4);
      } else if (marker1 == PAD) {
        // One PAD e.g. 3cQ[Pad]
        b3 = base64Alphabet[marker0];

        decodedData[encodedIndex] = (byte) (b1 << 2 | b2 >> 4);
        decodedData[encodedIndex + 1] = (byte) (((b2 & 0xf) << 4) | ((b3 >> 2) & 0xf));
      }
      encodedIndex += 3;
    }
    return decodedData;
  }

  /**
   * Discards any whitespace from a base-64 encoded block.
   *
   * @param data The base-64 encoded data to discard the whitespace from.
   * @return The data, less whitespace (see RFC 2045).
   */
  static byte[] discardWhitespace(byte[] data) {
    byte groomedData[] = new byte[data.length];
    int bytesCopied = 0;

    for (int i = 0; i < data.length; i++) {
      switch (data[i]) {
        case (byte) ' ':
        case (byte) '\n':
        case (byte) '\r':
        case (byte) '\t':
          break;
        default:
          groomedData[bytesCopied++] = data[i];
      }
    }

    byte packedData[] = new byte[bytesCopied];

    System.arraycopy(groomedData, 0, packedData, 0, bytesCopied);

    return packedData;
  }

  /**
   * Discards any characters outside of the base64 alphabet, per the
   * requirements on page 25 of RFC 2045 - "Any characters outside of the
   * base64 alphabet are to be ignored in base64 encoded data."
   *
   * @param data The base-64 encoded data to groom
   * @return The data, less non-base64 characters (see RFC 2045).
   */
  static byte[] discardNonBase64(byte[] data) {
    byte groomedData[] = new byte[data.length];
    int bytesCopied = 0;

    for (int i = 0; i < data.length; i++) {
      if (isBase64(data[i])) {
        groomedData[bytesCopied++] = data[i];
      }
    }

    byte packedData[] = new byte[bytesCopied];

    System.arraycopy(groomedData, 0, packedData, 0, bytesCopied);

    return packedData;
  }

  /**
   * Encodes a byte[] containing binary data, into a byte[] containing
   * characters in the Base64 alphabet.
   *
   * @param pArray a byte array containing binary data
   * @return A byte array containing only Base64 character data
   */
  public static byte[] encode(byte[] pArray) {
    return encodeBase64(pArray, false);
  }

  // public static String encode(String str) throws
  // UnsupportedEncodingException {
  // String baseStr = new String(encode(str.getBytes("UTF-8")));
  // String tempStr = Digest.digest(str).toUpperCase();
  // String result = tempStr + baseStr;
  // return new String(encode(result.getBytes("UTF-8")));
  // }

  public static String decode(String cryptoStr)
      throws UnsupportedEncodingException {
    if (cryptoStr.length() < 40)
      return "";
    try {
      String tempStr = new String(decode(cryptoStr.getBytes("UTF-8")));
      String result = tempStr.substring(40, tempStr.length());
      return new String(decode(result.getBytes("UTF-8")));
    } catch (ArrayIndexOutOfBoundsException ex) {
      ex.printStackTrace();
      return "";
    }
  }
}
